Author Correction: Roadmap for naming uncultivated Archaea and Bacteria

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Roadmap for naming uncultivated Archaea and Bacteria

The assembly of single-amplified genomes (SAGs) and metagenome-assembled genomes (MAGs) has led to a surge in genome-based discoveries of members affiliated with Archaea and Bacteria, bringing with it a need to develop guidelines for nomenclature of uncultivated microorganisms. The International Code of Nomenclature of Prokaryotes (ICNP) only recognizes cultures as 'type material', thereby preventing the naming of uncultivated organisms. In this Consensus Statement, we propose two potential paths to solve this nomenclatural conundrum. One option is the adoption of previously proposed modifications to the ICNP to recognize DNA sequences as acceptable type material; the other option creates a nomenclatural code for uncultivated Archaea and Bacteria that could eventually be merged with the ICNP in the future. Regardless of the path taken, we believe that action is needed now within the scientific community to develop consistent rules for nomenclature of uncultivated taxa in order to provide clarity and stability, and to effectively communicate microbial diversity.

A Grain Rot of Rice in Iran Caused by a Xanthomonas Strain Closely Related to X. sacchari

Rice grain rot disease was detected for the first time in Mazandaran Province, Iran. The bacteria isolated from infected rice plants showed grains rotted and darkening. A Xanthomonas strain closely connected to X. sacchari was identified using molecular and whole genome sequencing approaches confirmed as the causal agent by fulfilling Koch's postulates.

Pantoea rodasii sp. nov., Pantoea rwandensis sp. nov. and Pantoea wallisii sp. nov., isolated from Eucalyptus

Several Gram-negative-staining, facultatively anaerobic bacterial isolates were obtained from Eucalyptus seedlings showing symptoms of bacterial blight and dieback in Colombia, Rwanda and South Africa. Partial 16S rRNA gene sequencing, together with partial gyrB sequencing, placed the isolates in the genus Pantoea and indicated that they constituted three novel species. Multilocus sequence analysis (MLSA) based on partial sequences of gyrB, rpoB, infB and atpD revealed Pantoea dispersa , Pantoea eucrina and Pantoea cypripedii as their closest phylogenetic relatives. DNA–DNA hybridization studies confirmed the classification of the new isolates as three novel species and phenotypic tests allowed them to be differentiated from their closest phylogenetic neighbours. The names Pantoea rodasii sp. nov. [type strain LMG 26273T = BD 943T (deposited with the Plant Pathogenic and Plant Protecting Bacteria Collection, South Africa) = BCC 581T (deposited with the Bacterial Culture Collection, Forestry and Agricultural Institute, South Africa)], Pantoea rwandensis sp. nov. (type strain LMG 26275T = BD 944T = BCC 571T) and Pantoea wallisii sp. nov. (type strain LMG 26277T = BD 946T = BCC 682T) are proposed.

Hydrocarbon degradation, plant colonization and gene expression of alkane degradation genes by endophytic Enterobacter ludwigii strains

The genus Enterobacter comprises a range of beneficial plant-associated bacteria showing plant growth promotion. Enterobacter ludwigii belongs to the Enterobacter cloacae complex and has been reported to include human pathogens but also plant-associated strains with plant beneficial capacities. To assess the role of Enterobacter endophytes in hydrocarbon degradation, plant colonization, abundance and expression of CYP153 genes in different plant compartments, three plant species (Italian ryegrass, birdsfoot trefoil and alfalfa) were grown in sterile soil spiked with 1% diesel and inoculated with three endophytic E. ludwigii strains. Results showed that all strains were capable of hydrocarbon degradation and efficiently colonized the rhizosphere and plant interior. Two strains, ISI10-3 and BRI10-9, showed highest degradation rates of diesel fuel up to 68% and performed best in combination with Italian ryegrass and alfalfa. All strains expressed the CYP153 gene in all plant compartments, indicating an active role in degradation of diesel in association with plants.

Proposal to reclassify Brenneria quercina (Hildebrand and Schroth 1967) Hauben et al. 1999 into a new genus, Lonsdalea gen. nov., as Lonsdalea quercina comb. nov., descriptions of Lonsdalea quercina subsp. quercina comb. nov., Lonsdalea quercina subsp. iberica subsp. nov. and Lonsdalea quercina subsp. britannica subsp. nov., emendation of the description of the genus Brenneria, reclassification of Dickeya dieffenbachiae as Dickeya dadantii subsp. dieffenbachiae comb. nov., and emendation of the description of Dickeya dadantii

Bacterial isolates from oak trees in Spain and Britain, showing symptoms of bark canker and Acute Oak Decline (AOD), respectively, were examined by a polyphasic approach. Both 16S rRNA gene sequencing and multilocus sequence analysis (MLSA), based on partial sequences of gyrB, rpoB, infB and atpD genes, revealed that the isolates were separated into two genetic groups according to their origin. Their closest phylogenetic relative was Brenneria quercina, the causal agent of drippy nut disease of oak, which clustered distant to the other species of the genus Brenneria. MLSA data for species of the genera Brenneria, Pectobacterium, Dickeya, Erwinia, Pantoea and Samsonia confirmed the polyphyletic nature of the genus Brenneria and indicated synonymy of Dickeya dadantii and Dickeya dieffenbachiae. DNA-DNA hybridization experiments confirmed this synonymy and also revealed DNA-DNA relatedness values of 58-73% between the new oak isolates and B. quercina. Phenotypic and/or chemotaxonomic methods allowed B. quercina and the two genetic groups of new oak isolates to be discriminated from other recognized species of the genus Brenneria and from members of the closely related genera Dickeya, Pectobacterium and Samsonia. Based on the data obtained, the following taxonomic proposals are made: (1) reclassification of B. quercina as the type species of a novel genus, Lonsdalea gen. nov., as Lonsdalea quercina comb. nov. (type strain LMG 2724(T)=ATCC 29281(T)=CCUG 48867(T)=CFBP 3617(T)=CIP 105201(T)=DSM 4561(T)=ICMP 1845(T)), (2) classification of the oak isolates as Lonsdalea quercina subsp. iberica subsp. nov. (type strain LMG26264(T)=NCPPB 4490(T)) and Lonsdalea quercina subsp. britannica subsp. nov. (type strain LMG 26267(T)=NCPPB 4481(T)) and leading to the automatic creation of Lonsdalea quercina subsp. quercina subsp. nov. (type strain LMG 2724(T)=ATCC 29281(T)), (3) emendation of the description of the genus Brenneria, and (4) reclassification of Dickeya dieffenbachiae as Dickeya dadantii subsp. dieffenbachiae comb. nov. (type strain LMG 25992(T)=CFBP 2051(T)), with the automatic creation of Dickeya dadantii subsp. dadantii subsp. nov. (type strain LMG 25991(T)=CFBP 1269(T)).

Pantoea allii sp. nov., isolated from onion plants and seed

Eight yellow-pigmented, Gram-negative, rod-shaped, oxidase-negative, motile, facultatively anaerobic bacteria were isolated from onion seed in South Africa and from an onion plant exhibiting centre rot symptoms in the USA. The isolates were assigned to the genus Pantoea on the basis of phenotypic and biochemical tests. 16S rRNA gene sequence analysis and multilocus sequence analysis (MLSA), based on gyrB, rpoB, infB and atpD sequences, confirmed the allocation of the isolates to the genus Pantoea. MLSA further indicated that the isolates represented a novel species, which was phylogenetically most closely related to Pantoea ananatis and Pantoea stewartii. Amplified fragment length polymorphism analysis also placed the isolates into a cluster separate from P. ananatis and P. stewartii. Compared with type strains of species of the genus Pantoea that showed >97 % 16S rRNA gene sequence similarity with strain BD 390T, the isolates exhibited 11–55 % whole-genome DNA–DNA relatedness, which confirmed the classification of the isolates in a novel species. The most useful phenotypic characteristics for the differentiation of the isolates from their closest phylogenetic neighbours are production of acid from amygdalin and utilization of adonitol and sorbitol. A novel species, Pantoea allii sp. nov., is proposed, with type strain BD 390T ( = LMG 24248T).

Emended description of the genus Pantoea, description of four species from human clinical samples, Pantoea septica sp. nov., Pantoea eucrina sp. nov., Pantoea brenneri sp. nov. and Pantoea conspicua sp. nov., and transfer of Pectobacterium cypripedii (Hori 1911) Brenner et al. 1973 emend. Hauben et al. 1998 to the genus as Pantoea cypripedii comb. nov

Bacterial strains belonging to DNA hybridization groups (HG) II, IV and V, in the Erwinia herbicola-Enterobacter agglomerans complex, of Brenner et al. [Int J Syst Bacteriol 34 (1984), 45-55] were suggested previously to belong to the genus Pantoea, but have never been formally described and classified. Additionally, it has been shown in several studies that Pectobacterium cypripedii is more closely related to species of Pantoea than to those of Pectobacterium. In this study, the phylogenetic positions of Brenner's DNA HG II, IV and V and Pectobacterium cypripedii were re-examined by both 16S rRNA gene sequencing and multilocus sequence analyses (MLSA) based on the gyrB, rpoB, atpD and infB genes. The analyses revealed that DNA HG II, IV and V and Pectobacterium cypripedii form five separate branches within the genus Pantoea (strains from HG V were split into two branches). DNA-DNA hybridization data further confirmed that DNA HG II, IV and V constitute four separate species. Pectobacterium cypripedii was shown to be a close phylogenetic relative of Pantoea dispersa and DNA HG IV by both 16S rRNA gene sequence and MLSA analyses. Biochemical analyses performed on strains from DNA HG II, IV and V and Pectobacterium cypripedii confirmed their taxonomic position within the genus Pantoea and revealed phenotypic characteristics that allow the differentiation of these species from each other and from their closest phylogenetic neighbours. It is proposed to emend the description of the genus Pantoea and to describe Pantoea septica sp. nov. for DNA HG II (type strain LMG 5345(T) =BD 874(T) =CDC 3123-70(T)), Pantoea eucrina sp. nov. for DNA HG IV (type strain LMG 2781(T) =BD 872(T) =CDC 1741-71(T) =LMG 5346(T)), Pantoea brenneri sp. nov. for strains of DNA HG V excluding LMG 24534 (type strain LMG 5343(T) =BD 873(T) =CDC 3482-71(T)) and Pantoea conspicua sp. nov. for the remaining strain of DNA HG V (type strain LMG 24534(T) =BD 805(T) =CDC 3527-71(T)) and to transfer Pectobacterium cypripedii to the genus as Pantoea cypripedii comb. nov. (type strain LMG 2657(T) =ATCC 29267(T) =DSM 3873(T) =LMG 2655(T)).

Transfer of Pantoea citrea, Pantoea punctata and Pantoea terrea to the genus Tatumella emend. as Tatumella citrea comb. nov., Tatumella punctata comb. nov. and Tatumella terrea comb. nov. and description of Tatumella morbirosei sp. nov

Pantoea citrea, Pantoea punctata and Pantoea terrea were described for strains isolated from fruit and soil originating in Japan. These three 'Japanese' species have been shown to be phylogenetically distant from other species of the genus Pantoea. It has been observed previously that, using multilocus sequence analysis (MLSA), the 'Japanese' species consistently formed a distinct clade with an extended branch length, casting doubt on the inclusion of these species within the genus Pantoea. Furthermore, the 'Japanese' species are closely related to Tatumella ptyseos, strains of which originate from human clinical specimens. DNA-DNA hybridization and phenotypic tests confirmed the observed phylogenetic distance of P. citrea, P. punctata and P. terrea from the genus Pantoea and the affiliation of these species with Tatumella. In addition, strains causing pink disease of pineapple, identified previously as P. citrea , were shown to represent a separate species by using 16S rRNA gene sequence analysis, and MLSA and DNA-DNA hybridization data. The name Tatumella morbirosei sp. nov. with the type strain LMG 23360(T) (=BD 878(T)=NCPPB 4036(T)=CMC6(T)) is proposed to accommodate these strains. The new combinations Tatumella citrea (Kageyama et al. 1992) comb. nov. (type strain, SHS 2003(T)=ATCC 31623(T)=BD 875( T)=CCUG 30156(T)=CIP 105599(T)=DSM 13699(T)=JCM 8882(T)=LMG 22049(T)), Tatumella punctata (Kageyama et al. 1992) comb. nov. (type strain, SHS 2006(T)=ATCC 31626(T)=BD 876( T)=CCUG 30159(T)=CIP 105598(T)=DSM 13700(T)=JCM 8885(T)=LMG 22050(T)) and Tatumella terrea (Kageyama et al. 1992) comb. nov. (type strain, SHS 2008(T)=ATCC 31628(T)=BD 877(T)=CCUG 30161(T)=CIP 105600(T)=DSM 13701(T)=JCM 8887(T)=LMG 22051(T)) are proposed for P. citrea, P. punctata and P. terrea , respectively.

Pantoea vagans sp. nov., Pantoea eucalypti sp. nov., Pantoea deleyi sp. nov. and Pantoea anthophila sp. nov

Bacteria isolated from eucalyptus leaves and shoots showing symptoms of blight and die-back collected in Uganda, Uruguay and Argentina and from maize displaying brown stalk rot symptoms in South Africa were tentatively placed in the genus Pantoea on the basis of phenotypic and biochemical tests. These isolates, together with two strains (LMG 2558 and LMG 2560) previously assigned to Pantoea agglomerans based on protein electrophoregrams but later excluded from this species, were further investigated using molecular techniques. 16S rRNA gene sequencing and multilocus sequence analyses (MLSA) revealed that the strains were phylogenetically closely related to Pantoea agglomerans, Pantoea stewartii and Pantoea ananatis. MLSA and amplified fragment length polymorphism analysis placed the strains into four separate clusters, not containing any of the type strains of species of the genus Pantoea. DNA-DNA hybridization confirmed the classification of the isolates into four novel species, for which the names Pantoea vagans sp. nov. (type strain R-21566T=LMG 24199T=BCC 105T=BD 765T), Pantoea eucalypti sp. nov. (type strain R-25678T=LMG 24197T=BCC 076T=BD 769T), Pantoea deleyi sp. nov. (type strain R-31523T=LMG 24200T=BCC 109T=BD 767T) and Pantoea anthophila sp. nov. (type strain LMG 2558T=BD 871T=NCPPB 1682T) are proposed.

Functionally different isoforms of the human calcitonin receptor result from alternative splicing of the gene transcript

Two subtypes of the human calcitonin receptor (hCTR) have been described which differ from one another by the presence or absence of a 16-amino acid insert in the first intracellular loop. Both isoforms were stably expressed in baby hamster kidney cells to compare their ligand binding and second messenger coupling. The binding affinity and the on/off rate of binding for salmon CT were identical for the two receptor isoforms. However, the presence of the insert significantly reduced the ability of the receptor to couple to both adenylate cyclase and phospholipase C. Stimulation of a transient calcium response was only observed with the insert-negative receptor. Similarly, the ED50 for the cAMP response is 100-fold higher for the insert-positive form compared with the insert-negative form of the receptor. However, the maximal cAMP response was equivalent for both receptor isoforms. The rate of internalization of the insert-positive form of the receptor is significantly impaired relative to the insert-negative receptor, which suggests that this process may be dependent on the stimulation of a second messenger pathway. Cloning and characterization of the relevant portion of the hCTR gene revealed that these isoforms are generated by alternative splicing. We also discovered a third isoform of the hCTR, which can be generated by alternative splicing at the same position. The presence of a stop codon in this newly described alternative exon would lead to premature termination of the receptor at the C-terminal end of the first transmembrane domain.

Divergent structural requirements exist for calcitonin receptor binding specificity and adenylate cyclase activation

The basis of the high potency of salmon calcitonin (sCT) in radioligand binding competition and cAMP accumulation studies with cloned calcitonin (CT) receptors from rats, pigs, and humans was examined using two sets of CT analogues, i.e., chimeric sCT/human CT (hCT) analogues and analogues of sCT with differing capacities to form an amphipathic alpha-helix. In competition for 125I-sCT binding the following relative specificities were observed for the chimeric peptides: rat C1a CT receptor, sCT > or = (1-16)hCT/(17-32)sCT (ACT-15) > (1-16)sCT/(17-32)hCT (ACT-27); rat C1b CT receptor, sCT >> ACT-15 > ACT-27; hCT receptor, sCT = ACT-15 > ACT-27; porcine CT receptor, sCT > ACT-27 > ACT-15. In contrast, in ligand-induced cAMP accumulation studies the relative efficacies were as follows: rat C1a CT receptor, sCT = ACT-15 > ACT-27; rat C1b CT receptor, sCT = ACT-15 > ACT-27; hCT receptor, sCT = ACT-15 > or = to ACT-27; porcine CT receptor, sCT = ACT-15 = ACT-27. The data demonstrate that residues present in the carboxyl-terminal half of sCT are more important for binding competition with the rat C1a, rat C1b, and human CT receptors, whereas residues in the amino-terminal half of sCT are more important for binding competition with the porcine CT receptor. Carboxyl-terminal sCT residues are also important for full potency in adenylate cyclase activation with the rat C1a and rat C1b CT receptors but are less important for activation via the hCT receptor. The disparity in the relative potencies of the peptides in studies of binding competition and cAMP accumulation is suggestive of significant differences in the relative affinities of the peptides for active and inactive conformations of the CT receptor. The use of sCT analogues with varying capacities to form alpha-helices also revealed divergence in the responses of different receptors. This was most apparent for the stimulation of cAMP production by the rat receptor isoforms C1a and C1b. In cells expressing the C1a receptor, the helical analogues sCT and des-Ser2-sCT were equipotent with [Gly8]-des-Leu19-sCT and des-1-amino-[Ala1,7,Gly8]-des-Leu19 sCT, analogues that have reduced or absent helical structure, respectively. In contrast, the nonhelical analogues were 100-1000-fold less potent than sCT and des-Ser2-sCT at the C1b receptor. In general, reduction in the ability of sCT analogues to form helix structures had a greater impact on the potency of the analogues in competition for 125I-sCT binding than in cAMP accumulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium inflow in cells transfected with cloned rat and porcine calcitonin receptors

Ca2+ fluxes were examined in HEK 293 cells stably expressing the rat or porcine calcitonin receptors (CTRs). Calcitonin (CT) rapidly increased cytosolic Ca2+ ([Ca2+]i) concentrations in these cells in a manner which was sustained in the presence of extracellular Ca2+ ([Ca2+]e). In cells pretreated with CT, elevation of the [Ca2+]e concentration resulted in a further increase in [Ca2+]i which was concentration-dependent with respect to both the concentration of CT and the increment of [Ca2+]e. Untransfected cells, cells transfected with vector alone, and CTR-transfected cells not treated with CT, were unresponsive to [Ca2+]e. The microsomal Ca(2+)-ATPase inhibitor thapsigargin was able to mimic both the acute [Ca2+]i fluxes and responsiveness to [Ca2+]e mediated by CT in these cells. The CT-induced responsiveness to [Ca2+]e was neither mimicked by, nor affected by, activators of the cAMP or protein kinase C pathways. Treatment of cells with pertussis toxin influenced neither the primary Ca2+ fluxes in response to CT or thapsigargin nor the agonist-induced [Ca2+]e influx. Nifedipine failed to block responses to either CT or thapsigargin. These results lead to the important conclusion that the CTR participates in receptor-activated Ca2+ inflow, in which depletion of intracellular Ca2+ pools leads secondarily to influx of extracellular Ca2+.

Truncation of the porcine calcitonin receptor cytoplasmic tail inhibits internalization and signal transduction but increases receptor affinity

A series of mutant porcine calcitonin receptors with progressively truncated carboxy termini have been expressed in COS and HEK 293 cells. All forms of the receptor, including those totally lacking the cytoplasmic tail, were able to bind 125I-labeled salmon calcitonin. However, removal of C-terminal domains resulted in multiple functional changes in the receptor. First, compared with the wild type receptor, affinity of binding of salmon calcitonin was increased for truncated receptors, whether determined in intact transfected cells or in cell membranes. Second, internalization of the ligand-receptor complex was greatly attenuated for mutants truncated by 44 or 83 amino acids but not for an intermediate form truncated by 63 amino acids. Third, truncation affected signal transduction, which for the porcine calcitonin receptor occurs by generation of intracellular cAMP and Ca2+. The magnitude of adenylate cyclase responses was much reduced for the same mutants defective in internalization. Under conditions where expression of each receptor form was approximately equal, the magnitude of intracellular Ca2+ responses was decreased by C-terminal truncation. These results draw attention to the functional significance of the cytoplasmic tail of the porcine calcitonin receptor and suggest intramolecular interactions between the carboxy terminus and other receptor domains and/or cellular regulatory elements.

Isoforms of the rat calcitonin receptor: consequences for ligand binding and signal transduction

Two rat calcitonin (CT) receptor isoforms; C1a and C1b, are identical except for the presence of a 37-amino acid insert in the second extracellular domain of C1b. The functional consequences of this insert were examined after stable expression of these receptors into HEK-293 cells. In binding competition studies, dissociation of [125I]salmon CT ([125I]sCT) from C1b cells was rapid and complete, in contrast to dissociation from C1a cells, which was slow and incomplete, as seen with other CT receptor preparations. In these studies, C1a receptors displayed high affinity for salmon CT (Kd, 0.5 +/- 1.3 nM) and a slightly lower affinity for pig CT. Human CT competed more weakly for binding of [125I]CT. Although the relative affinities of the ligands were maintained for C1b receptors, the affinity for sCT was lower (Kd, 23 +/- 2 nM) and pig CT was approximately 10-fold less potent than sCT. Human and rat CT failed to compete with [125I]sCT even at 1 microM with the C1b receptor. Both receptors influence multiple effector systems, indicating coupling to multiple G-proteins. The CT peptides activated adenylate cyclase with relative efficacies consistent with the binding competition potencies. In addition, both receptor isoforms mediated a rapid increase in the levels of intracellular calcium after a CT challenge. These results show that an extracellular modification in the rat CT receptor results in altered ligand recognition as well as altered binding kinetics, but does not modify their ability to generate multiple second messengers.

Amylin is an agonist of the renal porcine calcitonin receptor

The cloned renal porcine calcitonin (pCT) receptor cDNA expressed by transient transfection in COS-1 cells or stable transfection in HEK-293 cells was assayed for interaction with CT, amylin, and CT gene-related peptide. Both [125I]salmon CT ([125I]sCT) and [125I]rat amylin displayed specific binding to transfected cells, and in both cases, pCT and rat amylin were equipotent in competing for binding. sCT was most potent in binding competition assays, whereas human CT and rat or human CT gene-related peptide did not compete. Despite the greater apparent affinity of sCT for receptor binding, sCT, pCT, and rat amylin had similar efficacies in stimulating the production of cAMP in the stably transfected cell line (EC50, 0.5-1.6 x 10(-9) M). These results contrasted with those obtained with the rat C1a CT receptor, for which amylin did not compete for [125I]sCT binding and stimulated cAMP production only at high concentrations. These results show that pCT and amylin interact with similar potencies with the pCT receptor and suggest that amylin may act as a natural ligand for this receptor.

Magnet retained overdentures using the Astra dental implant system

The Astra Implant System (AIS) is a biologically sound and simple way of providing stability for the complete lower denture where anatomical changes have made retention, stability and comfort difficult to achieve. An ongoing clinical study has been undertaken where 20 patients have been provided with magnet retained overdentures using this implant system. This represented a total of 70 implants placed. Seven implants were removed from four patients (three at exposure, one infection). The remaining implants have been followed up for 12 to 25 months and are considered to have achieved successful osseointegration. All the patients in the study are successfully wearing a lower denture retained by magnets. The overall success rate for the implants placed is 90% but if implants less than 9 mm in length are excluded from the results then the success rate is 97.7%.

Effect of autogenous bone grafts on healing following Le Fort I maxillary osteotomies

The healing of Le Fort I maxillary osteotomies was studied histologically in 12 adult rhesus monkeys to determine the effect of split autogenous rib grafts overlaying the osteotomy cuts on the lateral maxillary walls. The maxilla was advanced 8 mm in each animal, and examined at varying intervals up to 24 weeks after surgery. The results indicated that there were no obvious differences between the monkeys with and without the rib grafts. Both groups healed with good osseous union. It is concluded that autogenous rib grafts did not enhance bony healing.

Tooth pulp changes following Le Fort I maxillary osteotomy in a primate model

Le Fort I maxillary 'down-fracture' osteotomy with 8 mm advancement was performed in 15 adult rhesus monkeys. Forty-five tooth pulps were examined histologically at intervals from 0 to 24 weeks after surgery. Cell degeneration occurred in 31% of pulps examined, necrosis in 16% of pulps and osteo-dentine was found in 7% of pulps. Almost half of the teeth examined (47%) showed marked cellular changes, more frequently found in posterior teeth. Other features noted were inflammation (13%) and reactive dentine in pulps (24%). Axons degenerated initially but recovered by 24 weeks. It is concluded that Le Fort I maxillary osteotomy caused pulpal disturbances in an animal model and the extent to which this occurs in patients needs to be carefully monitored.

The versatility of hydroxyapatite blocks in maxillofacial surgery

There is considerable interest at present in the potential role of calcium hydroxyapatite as a biomaterial for bone augmentation in oral and maxillofacial surgery. Most of the published work has been on the particulate form, mainly in alveolar ridge procedures. However, hydroxyapatite is also available as solid or porous blocks. The blocks are more predictable in their use than are the particles, and are adaptable and versatile. This paper reviews the biological behaviour of the material and discusses the role of hydroxyapatite blocks in alveolar ridge augmentation and orthognathic surgery.

Biologic basis for interpositional autogenous bone grafts to the mandible

Interpositional autogenous bone grafting procedures were performed in the mandibles of 12 beagle dogs to assess cell survival within the graft and the superiorly repositioned alveolus, and to monitor the remodeling process. Histologic and radiologic results indicated that the grafts were well accepted and that new bone was rapidly laid down on their trabeculae. However, the osteocytes within the autografts generally did not survive. There was no evidence of necrosis of the superiorly displaced alveolus, nor any resorption of its surface cortex, and it rapidly united with the autograft and the mandible to produce a stable structure. This study confirms that the lingual pedicle of soft tissue is adequate to maintain the viability of the superiorly repositioned alveolus or segment and to allow rapid remodeling of the autogenous bone graft.

Hydroxyapatite as a bone substitute in the jaws

Densely sintered calcium hydroxyapatite has previously been shown to be biocompatible and stable. Its possible role in jaw surgery was investigated using a clinically analogous animal model. The apatite was implanted into the mandible of twelve dogs for 12 weeks, and the healing assessed radiologically and histologically. The new bone which was deposited directly onto the surface of the implants bonded them firmly to the adjacent tissues. There was no fibrous tissue between implant and bone. This material appears to be a suitable substitute for autogenous bone when used as inert 'space filler' in maxillo-facial surgical procedures.